Question: Rewrite the equation by completing the square. $x^{2}+10x+21 = 0$ $(x + $
Begin by moving the constant term to the right side of the equation. $x^2 + 10x = -21$ We complete the square by taking half of the coefficient of our $x$ term, squaring it, and adding it to both sides of the equation. Since the coefficient of our $x$ term is $10$, half of it would be $5$, and squaring it gives us ${25}$. $x^2 + 10x { + 25} = -21 { + 25}$ We can now rewrite the left side of the equation as a squared term. $( x + 5 )^2 = 4$